Need Help

[JHK]

I just got finished changing head gaskets and head bolts. I let it sit and idle about 30 min then took it for a test run, just drove normal. When I was about back to the shop I pushed it a little harder and it lost power and would not respond when i accelerated, then it died. I looked under the hood could not see any pipes off so I started it back up, still no power and now lots of white smoke. I am about to my wits end. Could someone please give me some kind of idea. Thanks